1. Field of the Invention:
The present invention is directed to an image forming apparatus system for selectively forming images on the basis of binary image data or multiple image data, and in particular, the present invention is directed to an image forming apparatus system preferably applied to an electrophotographic type optical printer such as a laser printer, a digital copying machine, a plain paper copier, a plain paper facsimile device, etc.
2. Description of the Background Art:
Generally, two types of image transmitting methods (1) and (2) as described below are used with respect to an image forming apparatus for forming an image by selectively transmitting binary image data and multiple image data from a LD (laser diode) writing-in control section to a LD control section.
(1) Method--1
The first method of transmitting image data is one in which a multiple value image data bus is employed. Furthermore, the first method utilizes only a transmission control system of clock synchronization by use of a clock signal in synchronism with image data on the multiple value image data bus.
As an example, a case of employing an 8-bit multiple image data bus ("00H": all lights, put out (off) . . . all "white"; "FFH": all lights, lighted up . . . all "black"; "01H"--"FEH": lighting up for halftone) is now explained. When the image data is multiple value data, the 256 values of "00H"--"FFH" are transmitted, as data, in synchronism with a clock. On the other hand, when the image data is binary value data, a white dot and a black dot are respectively transmitted as "00H" and "FFH" in a state of imaginary (dummy) multiple value data in synchronism with the clock.
(2) Method--2
The second method of transmitting image data is one in which a binary value image data bus is employed. Furthermore, the second method utilizes only the other transmission control system of clock synchronism not using the clock signal in synchronism with the image data on the binary value image data bus.
In a case that the image data is multiple value data, the respective dots are transmitted in a one-dot period with PWM (Pulse Width Modulation). On the other hand, in a case that the image data is binary value data, the white dots and the black dots are respectively transmitted on conditions of "all intervals, high level" and "all intervals, low level".
However, in a background digital copying machine or data complex machine, the type of image data to be processed at a time of writing data by the LD (laser diode) differs in each respective printing job. As an example, a case may arise of handling multiple value image data transmitted from a scanner after handling binary value image data from an application of a print controller or the like, or a case of the operations in reverse order may arise. As a result, a problem to be solved arises that the above-mentioned two methods (1) and (2) cannot be used widely for various (two, on this occasion) purposes in order to solve the subject matter both for the multiple value image data transmission and for the binary value image data transmission.
Furthermore, there arises another problem to be solved that in the background image forming apparatus of the electrophotographic type the laser diode is lit up outside of an image effective area in order to obtain a main scanning synchronization signal, and the output light signal obtained by lighting up the laser diode is detected by a sensor as a main scanning synchronization detecting signal. As a result, a state of the main scanning synchronization detecting signal exerts an adverse influence upon the image to be transmitted at the time of changing over the image data from the multiple value image data to the binary value image data, or vice versa. The above matter is also another problem to be solved.